1. Field of the Invention
This invention relates to labels generally, and more specifically but without limitation to deformable labels and to films for making such labels. In one aspect the invention relates to the use of such labels on squeezable or otherwise deformable substrates, where deformability and a resistance of the label to damage from cracking, tearing, creasing, wrinkling or shrinking due to deformation of the underlying substrate is desired. In another aspect the invention relates to such labels which possess the beneficial properties of the known polyethylene labels, but which exhibit improved dispensability and die-cuttability so that the labels may be conveniently applied to deformable substrates with modern labeling equipment.
2. Description of the Prior Art
In many label applications, it is desirable that the label stock from which the labels are cut from a film of polymeric material rather than paper. Polymeric film can provide properties lacking in paper, such as durability, strength, water resistance, abrasion resistance, gloss, transparency and other properties. Obviously, the polymeric material must meet the practical requirements of commercial manufacture and use. Material costs must be competitive. The film must be formable by a suitable commercial process such as cast film extrusion or blown film extrusion, requiring that the molten film material be flowable to the correct degree to accomplish proper film formation. The formed film must be capable of hot-stretching without deleterious effect, since it is generally advantageous to hot-stretch and anneal the formed film, so as to orient the film and impart a stiffness to the film that is different in machine and cross directions. The film must have a printable face and be die-cuttable and matrix-strippable when used in a pressure-sensitive label construction. The labels should have enough xe2x80x9cgivexe2x80x9d or flexibility to conform well to the substrates or containers on which they are used (a particularly demanding requirement when the labels are applied to flexible substrates such as squeezable plastic containers, for example shampoo bottles and condiment containers, but also a requirement with respect to rigid substrates which may have irregularities in their surfaces, such as glass bottles). On the other hand, labels cut from the film should be sufficiently dimensionally stable to maintain print registration and stiff enough to allow them to be properly dispensed as an in-mold label, or to dispense properly past a peel plate or peel-back edge, over which the liner or carrier is stripped, at speeds which are high enough to be commercially viable. Dispensing at these speeds generally requires a machine-direction (MD) stiffness of between 10 and 60 Gurley (as measured per TAPPI Gurley stiffness test T543pm). For good conformability, cross-direction (CD) Gurley should not exceed about 0.75 times MD Gurley.
Olefin blends have been found in many respects to be a preferred material to meet the demands of polymeric die-cut label manufacture. The relatively low cost of the olefinic resins, and their high strength allowing for low caliper film, tend to minimize overall material cost. Hot-stretched polypropylene and/or polyethylene provides stiffness in the machine direction even at relatively low-caliper thicknesses for adequate print registration and dispensing while providing sufficiently low tensile modulus and particularly sufficiently high elongation in the cross direction to allow good conformability.
Olefin blends have been found useful to produce, on an economical basis, printable 3.5 mil coextruded labels die-cut from biaxially hot-stretched film that are durable, strong and water-resistant, and that generally have good structural and surface properties and performance characteristics, and such labels have been manufactured and sold prior to the present invention. Biaxial stretching also makes an important contribution to performance by creating substantial differentials between machine direction (MD) and cross direction (CD) stiffnesses, tensile moduli, elongations, and other properties.
U.S. Pat. No. 4,837,075 discloses a label particularly adapted for use in in-mold labeling of blow-molded polyethylene containers comprising a heat activatable ethylene polymer adhesive layer and a surface printable layer with optional intermediate layers to provide interlayer adhesion and recycle of reground labels. The patent relates to labels, especially to labels that are particularly adapted for use in in-mold labeling of blow-mold polyethylene containers. More particularly, the patent relates to a coextruded plastic film label for use in such in-mold labeling applications. U.S. Pat. No. 4,837,075 is incorporated herein by reference.
U.S. Pat. No. 5,151,309 discloses a film facestock useful for making labels for use on deformable substrates, which labels are die-cuttable and dispensable, the film facestock including a layer of a polymer blend which includes an ethylenic material, a styrenic material, and a compatibilizing material. The patent relates to a compatibilized blend of certain styrenic materials and certain ethylenic materials, when used in the proper amounts to produce a film facestock of a given thickness, which provide a label with adequate resistance to cracking, tearing, creasing, wrinkling and shrinking upon deformation of a substrate to which the label is joined, with the printability, chemical and dimensional stability of previously known polyethylene labels while having the desirable die-cuttability and dispensability properties of the vinyl films. U.S. Pat. No. 5,151,309 is incorporated herein by reference.
U.S. Pat. No. 5,451,283 discloses extruded uniaxially oriented films useful in label manufacture and formed from blends of olefinic base materials and soft polar additives such as ethylene vinyl acetate (EVA) where the physical properties are changed in a directionally selective manner that improves abrasion resistance while preserving conformability by use of compatibilizers or coupling agents in the blends. Machine direction strength properties, including stiffness and tensile modulus, increase with little or no degradation of cross-direction elongation, and with limited degradation of cross-direction tensile modulus. The patent relates to the conformable labeling of flexible and rigid substrates such as squeeze bottles, glass bottles and the like, and to manufacture of die-cut labels for such uses from resinous film-forming materials which are blends of xe2x80x9csoftxe2x80x9d polar additives, such as ethylene vinyl acetate polymer (EVA), with low-cost olefinic base materials, particularly polypropylene, polyethylene, or combinations thereof. U.S. Pat. No. 5,451,283 is incorporated herein by reference.
U.S. Pat. No. 5,616,384 discloses an in-mold label material that is a nonwoven mat of fibers having one side fused with the outer surface of a polymeric container and the other side coated with a pigment-containing latex suitable for printing thereon. The label paper is manufactured from commercially available fibers combined in water into a homogeneous mixture and then formed into a mat employing a wet-lay process. For use with polyethylene containers, the label may be a web consisting of 88-100% polyethylene fibers and 0-15% polyvinyl alcohol fibers or 70-100% polyethylene fibers, 0-15% polyvinyl alcohol fibers and 0-30% polypropylene fibers. For use with polyester containers, the label may be a web consisting of 50-90% polyester staple fibers, 10-40% bicomponent polyester/co-polyester, core/sheath binder fibers and 0-10% polyvinyl alcohol binder fibers thermally bonded together. The nonwoven web of fibers has a pigmented coating. After the material has been cut into labels, the labels may be applied to the blow-molded containers in-mold without the use of an adhesive material using a conventional in-mold labeling technique or post-mold using adhesive. It is an object of the patent to provide a non-film polymeric label adapted to be used in-mold labeling of blow-molded containers made of polymeric material. U.S. Pat. No. 5,616,384 is incorporated herein by reference.
U.S. Pat. No. 5,849,419 discloses extruded uniaxially oriented films useful in label manufacture and formed from blends of olefinic base materials and soft polar additives such as ethylene vinyl acetate (EVA) where the physical properties are changed in a directionally selective manner that improves abrasion resistance while preserving conformability by use of compatibilizers or coupling agents in the blends. Machine direction strength properties, including stiffness and tensile modulus, increase with little or no degradation of cross-direction elongation, and with limited degradation of cross-direction tensile modulus. The patent relates to the conformable labeling of flexible and rigid substrates such as squeeze bottles, glass bottles and the like, and to manufacture of die-cut labels for such uses from resinous film-forming materials which are blends of xe2x80x9csoftxe2x80x9d polar additives, such as ethylene vinyl acetate polymer (EVA), with low-cost olefinic base materials, particularly polypropylene, polyethylene, or combinations thereof. U.S. Pat. No. 5,849,419 is incorporated herein by reference.
Plastic containers are used extensively in the packaging industry to carry fluids such as beverages, soap, cream, and oils. These containers are typically formed polyethylene, polypropylene, polyvinyl chloride, and other flexible plastics. The containers are deformable in their shape when a force is applied. When the force is removed, the containers return to their original shape. Conventional paper labels are not suitable for the deformable containers because paper labels can not deform with the containers and leave wrinkling and tearing during squeezing the containers. Plastic labels made of polyvinyl chloride, are deformable but are not good for the environment. The labels of this invention are deformable and are better for the environment than polyvinyl chloride labels.
One embodiment of this invention is a polymeric label comprising a core layer comprising at least about 50% by weight of a linear ethylene alpha-olefin copolymer and at least about 5% by weight of a propylene copolymer, and a skin layer comprising a propylene copolymer.
Another embodiment of this invention is a polymeric label applied to a squeezable plastic container comprising a core layer comprising at least about 50% by weight of a linear ethylene alpha-olefin copolymer and at least about 5% by weight of a propylene copolymer, and a skin layer comprising a propylene copolymer.
Advantages of the polymeric label include one or more of the following:
1. When attached to a squeezable plastic container, the label is deformable with the container when the container is squeezed.
2. When attached to a squeezable plastic container, the label does not wrinkle when the container is squeezed.
3. When attached to a squeezable plastic container, the label does not tear when the container is squeezed.
4. A label material that is better for the environment than a polyvinyl chloride label.
5. A label that can be recycled with the plastic container without having to be removed.